Bacteriocins are a kind of antimicrobial peptides that kill or inhibit the growth of bacterial strains. The purpose of this study was to investigate the antibacterial effect of Serratia marcescens on several pathogenic bacterial strains. Bacteriocin produced by S. marcescens was purified by chromatography with Sephadex G-75 column, and its antibacterial effect on gram-negative bacteria, including Escherichia coli ATCC 700928, Pseudomonas aeruginosa PTCC 1707, S. marcescens PTCC 1621, Vibrio fischeri PTCC 1693, and Vibrio harveyi PTCC 1755, were evaluated by the disk diffusion method. The structure of bacteriocin was determined by nuclear magnetic resonance spectroscopy. The interaction of bacteriocin with the antigen 43 (Ag43) of E. coli was evaluated by the molecular docking method. Bacteriocin extracted from bacterial isolates had antibacterial activity on E. coli strains but not on other studied strains. Bioinformatics analysis also showed bacteriocin docking with Ag43 with an energy of -159.968 kJ/mol. Natural compounds, such as bacteriocin, can be an alternative to common chemical compounds and antibiotics. To reach a definite conclusion in this regard, there is a need for further research and understanding of their mechanism of action.

Objective(s): The current study aimed to investigate the control and treatment of biofilm-producing isolates of Pseudomonas aeruginosa using silicon nanoparticles (SiNPs). Materials and Methods: Biofilm-producing isolates of P. aeruginosa were recovered from various food samples and identified through fluorescent green colony formation on selective and differential media, as well as the amplification of oprI and oprL genes. Tube methods, Congo-red agar method, and scanning electron microscopy (SEM) were used to study biofilm phenotypes. The effect of SiNPs was evaluated by broth dilution assay. Results: The biofilm assay revealed that these isolates formed biofilms on glass surfaces within 72 hr of incubation. Scanning electron micrographs showed that the biofilm communities were composed of multicellular clusters of P. aeruginosa encased in matrix material. However, these isolates were unable to form biofilms on SiNPs-coated surfaces. The results showed that the planktonic isolates of P. aeruginosa were comparatively sensitive to the antibacterial properties of SiNPs, with minimum inhibitory concentration (MIC) ranging from 100 to 200 µg/ml. Contrarily, the biofilms were found to be 500 times more tolerant to the highest concentration of SiNPs (MIC of 500 µg/ml) and were more resistant. Under static conditions, the sedimentation of SiNPs resulted in their ineffectiveness. However, under shaking conditions, the biofilms were effectively dispersed and the cells were lysed. The results showed that SiNPs were effective against both the planktonic and the metabolically inactive forms of P. aeruginosa. Conclusion: This study suggests that SiNPs could be a useful tool for preventing the formation of biofilms and removing pre-existing biofilms.

A new series of derivatives of N, 2-diphenylquinazolin-4-amine (3a-g) was synthesized through nucleophilic substitution. The structures of compounds were characterized by FTIR, 1H-NMR, and 13C-NMR spectroscopy. All synthesized compounds were evaluated for their antimicrobial activities against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Lactobacillus rhamnosus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria and also for antifungal activities, against Candida albicans, using broth microdilution method to determine their minimum inhibitory concentrations (MIC). Most of the compounds have shown moderate to good antibacterial activities, significantly compound 3g at 0. 0625 mg/mL concentration had the highest activity against P. aeruginosa. Also, the MIC of compound 3f was 0. 0078 mg/mL against S. aureus. Furthermore, the tested compounds exhibited remarkable antifungal activities against C. albicans, significantly compounds 3c and 3g showed the least MIC (equal to 0. 0625 mg/mL). Also, a docking study into DNA gyrase has been made for these compounds. The synthesized compounds showed dock score values between-3. 05 and-6. 13kcal/mol. The highest dock score among them was-6. 13 kcal/mol, found for compound 3c.

Some bacteria commonly found on plants can catalyze the freezing of water at a higher temperature than others, at or near 0 °C. The freezing point of pure water is about -40 °C and is initiated by creating ice nucleations. However, when ice nucleation proteins (INPs) are present, ice nucleations form at temperatures close to or above 0 °C. INPs are often attached to the outer membrane by a phosphatidylinositol anchor and are sometimes secreted extracellularly. The monomers of INPs in Pseudomonas syringae are 120 to 180 kDa. INP has three domains, and the central domain is highly repetitive. The central domain consists of the consensus sequence of eight amino acid repeats. Eight amino acid repeats create a 16-residue fragment, and three 16-residue fragments form the 48-residue fragment. Studies have shown that INPs may have a β-helical fold and interact with water through the repetitive motif. Most ice nucleation bacteria are gram-negative, including P. syringae, Pseudomonas viridiflava, Pseudomonas fluorescens, Xanthomonas compestris, Erwinia ananas, and Erwinia herbicola. For optimum protein activity, the presence of the complete bacterial cell is essential. INPs are influential in different aspects, including snowmaking, agriculture, freeze-concentration in the food industry, signal transduction, atmospheric applications as cloud condensation nuclei, and surface display (expression of a foreign protein on the cell surface for biotechnological purposes). This study provides a brief overview of ice nucleation proteins and their applications since ice nucleation is an important phenomenon that affects various aspects, from climate to biological systems.

In this study, a novel bicomponent nanomaterial has been designed to be used as an antibacterial effective wound dressing for dry wounds. These nanofibers' wound dressing successfully have been produced by coaxial electrospinning method feeding neat polylactic acid into the core and thermoplastic polyurethane-silver nanoparticles into the shell. In addition to examining the antibacterial and cytotoxicity properties of the designed polymeric nanomaterials, physical and chemical characterization studies have been also carried out. It has been determined that the 10% silver nanoparticles doped bicomponent nanomaterial had the thinnest smooth nanofibers with 1127 nm value, the highest hydrophobic behavior with 131° contact angle value, the highest tensile strength with 2.53 MPa value, and the highest flexibility with 66.84% value. In addition, 10% and 5% silver nanoparticles doped bicomponent nanofibers have been indicated to have high cell viability with values of about 90% and 80% respectively. It has been emphasized that these bicomponent electrospun mats, which have been improved for dry wounds can be used as a 100% antibacterial effective wound dressing against escherichia coli, staphylococcus aureus, and Pseudomonas aeruginosa if it is renewed every 24 hours.

Today, the idea of ​​using biodegradable polymers which can naturally replace skin shortly before skin repair while also inhibiting the growth of bacteria causing wound infection is of great interest. The purpose of this study was to investigate the possibility of making degradable films using natural compounds, including chicken gelatin and collagen, henna plant extract, and aloe vera gel. Materials and Methods: Aloe vera gel and ethanolic extract of the henna plant were prepared and their antioxidants were studied by DPPH (Diphenylpicrylhydrazyl) free radical-scavenging assay. Then, the antimicrobial properties of henna extract and aloe vera gel were evaluated against Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans using the disk diffusion method along with the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. To prepare the films, the gelatin and collagen extracted from chicken, along with the ethanolic extract of henna and aloe vera gel, was used. Subsequently, the physicochemical and mechanical properties (elasticity, dissolution potency, and moisture level and microscopy investigation) of the films as well as the antimicrobial properties of films against these microbes were investigated. Results: The results revealed that the anti-microbial effects of henna extract and aloe vera gel alone and in combination with gelatin/collagen matrix varied and had different effects on the tested microbes. Moreover, aloe vera showed stronger antioxidant properties than henna. Conclusion: When synthesizing gelatin/collagen-based biopolymers, plant compounds and extracts can be used to enhance the antioxidant and antibacterial properties and apply organic band aids to help heal wounds and prevent wound infections

Introduction: The main objective of this study was to determine the chemical composition of the aerial part of the essential oil and the hydrosol extract of Inula viscosa which has never been studied and to compare their antioxidant, anti-inflammatory, and antimicrobial properties in vitro. This was done in order to identify new biologically active agents.Materials and Methods: The essential oil and hydrosol extract were analyzed by GC and GC/MS. Antimicrobial activity was tested against three bacteria and two fungi. The antioxidant activities were assessed using three different methods: radical scavenging activity (DPPH), the β-carotene bleaching test, and Ferric-Reducing Antioxidant Power (FRAP). The anti-inflammatory activity was assessed using the protein denaturation method.Results: The essential oil of Inula viscosa was composed mainly of hydrocarbon sesquiterpenes (52.6%) and oxygenated sesquiterpenes (47.0%), while the hydrosol extract was mainly composed of oxygenated sesquiterpenes (86.6%). The results of the biological activities showed that the hydrosol extract exhibited an interesting antioxidant activity, nearly equivalent to the synthetic antioxidant BHT. Furthermore, the hydrosol extract displayed very good anti-inflammatory activity, with an IC50 of 0.51 g/L, in comparison to diclofenac sodium (IC50 = 0.63 g/L). The hydrosol extract also exhibited antimicrobial activity and acted as an effective inhibitor of Bacillus cereus, Pseudomonas aeruginosa, Candida ATCC 26960, and Candida ATCC 10231 microorganisms.Conclusions: The hydrosol extract of I. viscosa make this specie a potential alternative natural for use in the food and pharmaceutical industries. It can be utilized in the treatment of diseases involving oxidative stress as well as in the treatment of microbial and inflammatory infections.